Not Applicable
This invention relates to a medical device delivery systems. More particularly the present invention is directed to stent delivery systems which employ stent retaining sleeves which retain the stent to the catheter prior to delivery of the stent into a body vessel. The present invention provides for a stent delivery system wherein the stent retaining sleeves are composed at least partially of a film of expanded or skived polytetrafluoroethylene (hereinafter PTFE). Other inventive aspects of the present delivery system will be made apparent below.
Stents and stent delivery assemblies are utilized in a number of medical procedures and situations, and as such their structure and function are well known. A stent is a generally cylindrical prosthesis introduced via a catheter into a lumen of a body vessel in a configuration having a generally reduced diameter and then expanded to the diameter of the vessel. In its expanded configuration, the stent supports and reinforces the vessel walls while maintaining the vessel in an open, unobstructed condition.
Both self-expanding and inflation expandable stents are well known and widely available in a variety of designs and configurations. Self-expanding stents must be maintained under positive external pressure in order to maintain their reduced diameter configuration during delivery of the stent to its deployment site. Inflation expandable stents are crimped to their reduced diameter about the delivery catheter, maneuvered to the deployment site, and expanded to the vessel diameter by fluid inflation of a balloon positioned on the delivery catheter. The present invention is particularly concerned with delivery and deployment of inflation expandable stents, although it is generally applicable to self-expanding stents when used with balloon catheters.
In advancing an inflation expandable stent through a body vessel to the deployment site, there are a number of important considerations. The stent must be able to securely maintain its axial position on the delivery catheter, without translocating proximally or distally, and especially without becoming separated from the catheter. The stent, particularly its distal and proximal ends, must be protected to prevent distortion of the stent and to prevent abrasion and/or reduce trauma of the vessel walls.
Inflation expandable stent delivery and deployment assemblies are known which utilize restraining means that overlie the stent during delivery. U.S. Pat. No. 4,950,227 to Savin et al, relates to an expandable stent delivery system in which a sleeve overlaps the distal or proximal margin (or both) of the stent during delivery. During expansion of the stent at the deployment site, the stent margins are freed of the protective sleeve(s). U.S. Pat. No. 5,403,341 to Solar, relates to a stent delivery and deployment assembly which uses retaining sheaths positioned about opposite ends of the compressed stent. The retaining sheaths of Solar are adapted to tear under pressure as the stent is radially expanded, thus releasing the stent from engagement with the sheaths. U.S. Pat. No. 5,108,416 to Ryan et al., describes a stent introducer system which uses one or two flexible end caps and an annular socket surrounding the balloon to position the stent during introduction to the deployment site.
As previously stated, the present invention is particularly concerned with the delivery and deployment of inflation expandable stents. As such, the present invention is also directed to stent delivery catheters which have an expandable portion(s) or balloon(s), wherein the balloon may have a stepped compliance curve. In a preferred embodiment of the invention the stent delivery system employs a balloon which has a portion or portions which are characterized as having a stepped compliance curve and other portion or portions which have a linear compliance curve to burst pressure. In the embodiment where the balloon has a stepped compliant portion any sleeve material may be used. An example of sleeves which may be used with a stepped compliant balloon according to the present invention are disclosed in U.S. Pat. No. 4,950,227 to Savin et al, the entire contents of which is hereby incorporated by reference.
An example of a balloon having the preferred stepped compliant characteristics described above is disclosed in U.S. Pat. No. 5,749,851 to Wang. U.S. Pat. Nos. 5,843,116 and 5,645,560 to Crocker et al. The Crocker et al. references describe balloons which may also be used with the preferred embodiment of the stent delivery system as described above.
The entire content of all of the patents listed within the present patent application are incorporated herein by reference.
This invention provides for a stent delivery system which includes a catheter, a stent mounting region, a stent mounted thereupon, and one or more stent retaining sleeves. The stent mounting region may be located about a balloon or inflatable portion of the catheter. A stent which is mounted to the stent mounting region may be self-expanding, such as a NITINOL shape memory stent, or it may be expandable by means of the expandable portion of the catheter or balloon. The stent is held in place around the stent mounting region prior to percutaneous delivery of the stent by means of one and preferably two end sleeves which are composed, at least partially of a film of PTFE.
The end sleeves may be solid tubes of extruded and shaped PTFE; a tube of PTFE and any thermoplastic elastomer material in combination; or a sectionally diverse tube having portions which are exclusively PTFE, thermoplastic polymer(s), or any combination thereof. In a preferred embodiment, a combination PTFE and thermoplastic elastomer sleeves may be heat shrunk to the catheter and stent when the present stent delivery system is in the reduced or predelivery state. In yet another preferred embodiment, the balloon or inflatable portion of the catheter may have one or more portions characterized as being stepped compliant.